Quick-coupling devices are known for sealably connecting a tube in a stepped bore of a rigid element. In general, that kind of device is in the form of a tubular insert comprising a tubular body having means for anchoring it permanently in the rigid element and means for retaining the tube. Usually, the anchoring means are implemented in the form of Christmas-tree shaped teeth formed on the outside face of the tubular body and opposing axial withdrawal of the body once the body has been inserted inside a first section of the bore in the rigid element. The tube-retaining means may be implemented in the form of a washer having inside teeth which are flexibly raised while the tube is being inserted and which tend to bite into the tube to oppose extraction thereof, or it may be in the form of a fastening ring comprising a plurality of longitudinal arms whose free ends have edges directed towards the outside surface of the tube and which co-operate via a camming surface with the tubular body so as to be clamped against the tube when it is pulled in the extraction direction. Between the tube and the body there may also exist a sliding pusher for raising the teeth so as to allow the tube to be disconnected. Prior to mounting in the rigid element, the coupling device is in the form of a "cartridge", i.e. the insert is pre-fitted internally with the tube-retaining means, and it is mounted in the rigid element merely by being forced into the stepped bore.
The coupling is sealed by means of a gasket, generally an O-ring, which is housed in a second section of the bore while the tubular body is being inserted inside the first section of the bore, the second section being of smaller diameter than the first. In general, the bore has a third section of even smaller diameter than the second section, and close to the outside diameter of the tube, which third section is intended to receive the end of the tube so as to position it properly.
At present, the above device is installed inside the bore by means of a special assembly tool in the form of a tubular sleeve which forces the tubular body to penetrate into the bore. A circularly symmetrical elongate part passes through the tubular body, and at one end it includes a shoulder which bears against an end of the tubular body while at its other end it has a groove in which the gasket is housed. On assembly, while the tubular body is being inserted inside the bore, the sealing ring is put into the second section of the bore and the elongate part is withdrawn.
Nevertheless, during storage and transport and during the various handling operations to which the couping device is subjected prior to assembly, the gasket is unprotected and may be damaged, or may even escape from the part on which it is held. Similarly, during assembly, since the outside diameter of the gasket is greater than the diameter of the second section of the bore, the ring rubs against the inlet edge of the second section and thus again runs the risk of being damaged.
It therefore seems appropriate to design a "cartridge" type quick-coupling device having means for protecting the gasket effectively both before and during assembly.